/**
 * Copyright (c) 2010, Daniel Bimschas and Dennis Pfisterer, Institute of Telematics, University of Luebeck
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 	- Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * 	  disclaimer.
 * 	- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 * 	  following disclaimer in the documentation and/or other materials provided with the distribution.
 * 	- Neither the name of the University of Luebeck nor the names of its contributors may be used to endorse or promote
 * 	  products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package de.uniluebeck.itm.nettyprotocols.isense.otap;

import com.coalesenses.tools.iSenseAes;
import com.coalesenses.tools.iSenseAes128BitKey;
import de.uniluebeck.itm.nettyprotocols.isense.iseraerial.ISerAerialOutgoingPacket;
import de.uniluebeck.itm.nettyprotocols.util.HandlerTools;
import de.uniluebeck.itm.nettyprotocols.isense.otap.generatedmessages.*;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelDownstreamHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ISenseOtapPacketEncoder extends SimpleChannelDownstreamHandler {

	private final Logger log;

	private iSenseAes aes = null;

	public ISenseOtapPacketEncoder() {
		this(null);
	}

	public ISenseOtapPacketEncoder(String instanceName) {
		log = LoggerFactory.getLogger(instanceName != null ? instanceName : ISenseOtapPacketEncoder.class.getName());
	}

	private byte[] computeCrc(byte[] payload) {
		byte crc[] = {(byte) 0xAA, (byte) 0xAA, (byte) 0xAA, (byte) 0xAA};

		for (int i = 0; i < payload.length; i++) {
			crc[i % 4] = (byte) (0xFF & (crc[i % 4] ^ payload[i]));
		}

		return crc;
	}

	@Override
	public void writeRequested(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		Object msg = e.getMessage();

		if (msg instanceof ISenseOtapPacketEncoderSetAESKeyRequest) {

			iSenseAes128BitKey key = ((ISenseOtapPacketEncoderSetAESKeyRequest) msg).getKey();

			if (key != null) {
				log.info("Encrypting payload of otap packets");
				this.aes = new iSenseAes(key);
			} else {
				log.info("Disabled otap payload encryption");
				this.aes = null;
			}

			return;
		}

		byte[] bytes = null;

		if (msg instanceof OtapInitReply) {
			bytes = MacroFabricSerializer.serialize((OtapInitReply) msg);
		} else if (msg instanceof OtapInitRequest) {
			bytes = MacroFabricSerializer.serialize((OtapInitRequest) msg);
		} else if (msg instanceof OtapProgramReply) {
			bytes = MacroFabricSerializer.serialize((OtapProgramReply) msg);
		} else if (msg instanceof OtapProgramRequest) {
			bytes = MacroFabricSerializer.serialize((OtapProgramRequest) msg);
		} else if (msg instanceof PresenceDetectRequest) {
			bytes = MacroFabricSerializer.serialize((PresenceDetectRequest) msg);
		} else if (msg instanceof PresenceDetectReply) {
			bytes = MacroFabricSerializer.serialize((PresenceDetectReply) msg);
		}

		if (bytes != null) {

			if (aes != null) {
				log.trace(("Encrypted otap payload wit AES"));
				bytes = aes.encodeWithRandomNonce(bytes);
			}

			ISerAerialOutgoingPacket iSerAerialPacket =
					new ISerAerialOutgoingPacket(ISerAerialOutgoingPacket.BROADCAST_ADDRESS_16_BIT, (byte) 0x0,
							ChannelBuffers.wrappedBuffer(bytes, computeCrc(bytes))
					);

			log.trace("Encoded {} otap packet with crc: {}", msg.getClass().getSimpleName(), iSerAerialPacket);

			HandlerTools.sendDownstream(iSerAerialPacket, ctx);
		} else {
			super.writeRequested(ctx, e);
		}

	}
}
